Thermoplastic resin composition

ABSTRACT

A thermoplastic resin composition of high heat resistance and high impact resistance is described, comprising: (A) 50 to 90% by weight of a copolymer prepared by copolymerization of 10 to 35% by weight of acrylonitrile, 60 to 85% by weight of a monomer mixture of 2-isopropenylnaphthalene (2-IPN) and α-methylstyrene (α-MeSt), the proportion of 2-IPN being 5 to 70% by weight based on the total weight of 2-IPN and α-MeSt, and 0 to less than 10% by weight of a vinyl monomer copolymerizable with the foregoing monomers; and (B) 10 to 50% by weight of a graft copolymer prepared by polymerizing 15 to 50 parts by weight of at least one monomer selected from the group consisting of aromatic vinyl compounds, vinyl cyanides, methacrylic acid alkyl esters, and acrylic acid alkyl esters in the presence of 50 to 85 parts by weight of a butadiene- or alkyl acrylate-based rubber, the sum of the graft and rubber components being 100 parts by weight.

RELATED APPLICATIONS

This application s a divisional application of U.S. application Ser. No.834,122 filed on Feb. 26, 1986, now U.S. Pat. No. 4,701,495 which inturn is a continuation application of U.S. application Ser. No. 618,663filed June 8, 1984, now abandoned.

FIELD OF THE INVENTION

The present invention relates to a novel thermoplastic resin compositionhaving superior heat resistance and impact resistance.

BACKGROUND OF THE INVENTION

A rubber/an acrylonitrile-styrene copolymer composition (hereinaftersometimes referred to as "ABS resin") is widely used because of its goodworkability and superior impact resistance. This ABS resin, however, hasa disadvantage of being poor in heat resistance which is usuallyexpressed in terms of a heat distortion temperature. In order toovercome the foregoing problem, various methods have been proposed,including:

(1) a method of substituting α-methylstyrene (hereinafter sometimesabbreviated to "α-MeSt") for styrene (hereinafter sometimes abbreviatedto "St") of the components to be grafted onto rubber, i.e., St. andacrylonitrile (hereinafter sometimes abbreviated to "AN"); see U.S. Pat.No. 2,908,661;

(2) a method of blending an α-MeSt/AN copolymer with an ABS resin; seeJapanese Patent Publication No. 18194/60;

(3) a two-stage grafting method in which St and AN are first graftedonto rubber and then α-MeSt and AN are grafted thereonto; see JapanesePatent Publication No. 13616/67;

(4) a method of blending an α-MeSt-methyl methacrylate (hereinaftersometimes abbreviated to "MMA")-AN copolymer to an ABS resin; seeJapanese Patent Publication Nos. 18016/70, 33304/70 and 15902/69; and

(5) a composition comprising an α-MeSt-MMA-AN copolymer and a graftcopolymer prepared by graft-polymerization of MMA, St and AN ontorubber; see Japanese Patent Publication No. 37415/71.

Substitution of α-MeSt and MMA for conventional resin components enablesthe artisan to increase heat resistance to a certain extent but not to asufficient level. Thus, the resulting resin compositions are limited intheir use. For this reason, it has been desired to develop an ABS resinhaving a more improved heat resistance.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a thermoplastic resincomposition which has superior heat resistance that could not beexpected for conventional heat resistant or super heat resistant ABSresins and, furthermore, which is superior in impact resistance andworkability.

It has been found according to the present invention that compositioncomprising: (A) a 2-isopropenylnaphthalene (hereinafter sometimesabbreviated to "2-IPN")-α-MeSt-AN copolymer; and (B) a graft copolymeras an impact strength-increasing agent which is prepared bygraft-polymerizing a monomer mixture of one or more of aromatic vinylcompounds, vinyl cyanide, methacrylic acid alkyl esters, and acrylicacid alkyl esters onto a diene-based rubber or alkyl acrylate-basedrubber possesses superior heat resistance and impact resistance.

The present invention relates to a thermoplastic resin compositioncomprising:

50 to 90% by weight of a copolymer (A) prepared by copolymerization of10 to 35% by weight of acrylonitrile, 60 to 85% by weight of a monomermixture consisting of 2-isopropenylnaphthalene and α-methylstyrene, theproportion of 2-isopropenylnaphthalene being 5 to 70% by weight based onthe total weight of 2-isopropenylnaphthalene and α-methylstyrene, and 0to less than 10% by weight of a vinyl monomer copolymerizable with theforegoing monomers; and

10 to 50% by weight of a graft copolymer (B) prepared by polymerizing 15to 50 parts by weight of at least one monomer selected from the groupconsisting of aromatic vinyl compounds, vinyl cyanide, methacrylic alkylesters, and acrylic alkyl esters in the presence of 50 to 85 parts byweight of a butadiene-based rubber or alkyl acrylate-based rubber, thesum of the rubber and graft components being 100 parts by weight.

DETAILED DESCRIPTION OF THE INVENTION

One of the features of the present invention is to provide athermoplastic resin composition having superior heat resistance. Sincethe thermoplastic resin composition of the present invention is composedmainly of the copolymer (A) containing 2-IPN, i.e., a 2-IPN-MeSt-ANcopolymer exhibits a considerably increased heat resistance thanconventional copolymer compositions not containing 2-IPN, such asα-MeSt-An and α-MeSt-St-AN. Thus, it can be seen that the effect of the2-IPN component on the heat resistance of the composition issurprisingly significant.

Another feature of the present invention is that the thermoplastic resincomposition of the present invention has superior impact resistance.2-IPN-containing copolymers per se are superior in heat resistance butare poor in impact strength and, thus, are of little practical value.Addition, however, of the graft copolymer (B) as an impactstrength-increasing agent of the copolymer (A), the graft copolymer (B)being prepared by adding a monomer mixture of one or more of aromaticvinyl compounds, vinyl cyanide, methacrylic acid alkyl esters, andacrylic acid alkyl esters, to a butadiene-based rubber or alkylacrylate-based rubber latex having a large mean particle size and thenpolymerizing the resulting mixture, results in the formation of acomposition having superior impact resistance.

Still another feature of the present invention is that the meltviscosity of the composition can be easily controlled, for example, byadjusting the degree of polymerization of the copolymer (A) by the useof a chain transfer agent.

The present invention will hereinafter be explained in detail. First,the copolymer (A) of 2-IPN, α-MeSt and AN, which is a main component ofthe thermoplastic resin composition of the present invention, isdescribed. The copolymer (A) endows the composition with physicalproperties such as heat resistance, hardness and tensile strength. As apractical matter, of course, these physical properties vary depending onthe monomer composition of the copolymer (A).

2-IPN is an important component that among the above-described threecomponents, most greatly contributes to heat resistance. α-Methylstyreneis also a component contributing to heat resistance. Although the totalamount of 2-IPN and α-methylstyrene is desired to be as large aspossible in increasing the heat resistance of the composition, if thecontent is too large, the yield in the copolymerization will drop. Theproportion of the sum of the 2-IPN and α-MeSt in the monomer mixture isfrom 60 to 85% by weight and preferably from 65 to 80% by weight. If theproportion is less than 60% by weight, heat resistance cannot beincreased, whereas if it is in excess of 85% by weight, the yieldundesirably decreases. 2-IPN, when used in combination with α-MeSt, canprovide higher heat resistance than α-MeSt alone. The proportion of2-IPN is from 5 to 70% by weight, preferably from 10 to 60% by weight,based on the total weight of 2-IPN and α-MeSt. If the proportion of2-IPN is less than 5% by weight, the desired high heat resistance cannotbe obtained, whereas if it is in excess of 705 by weightpolymerizability is somewhat reduced.

In the preparation of the copolymer (A), it is preferred to employ anemulsion polymerization method in order that the amounts of 2-IPN andα-MeSt contributing to heat resistance are increased as much as possibleand, furthermore, the rate of polymerization and yield are increased.Acrylonitrile has the effects of increasing the polymerizability of themonomer mixture in the emulsion polymerization and, furthermore, ofincreasing the impact strength and resistance to thermal decompositionof the copolymer (A). However, when used in large amounts, acrylonitrilecauses a reduction in heat resistance. Acrylonitrile, therefore, is usedin a proportion of from 10 to 35% by weight and preferably from 15 to30% by weight.

Vinyl monomers copolymerizable with the above-described monomers includestyrene, methyl methacrylate methacrylonitrile, methacrylic acid, andacrylic acid, etc. This vinyl monomer can be used in small amounts ifnecessary to improve a rate of polymerization and to provide otherproperties. Usually it is used in an amount of 0 to less than 10% byweight.

In the preparation of the copolymer (A), as described above, it is mostpreferred to employ emulsion polymerization. This emulsionpolymerization can be performed by known procedures using peroxides,emulsifying agents, polymerization accelerators, and so forth. Theemulsion polymerization process may be performed in any suitable manner.For example, the monomer mixture is added at the same time to thereaction system and polymerized, or the monomer mixture is divided andadded in several portions, or one or more monomer mixtures arecontinuously introduced into the reaction system and polymerized. Forthis purpose of adjusting the degree of polymerization (molecularweight) of the copolymer (A), a chain transfer agent, such asmercaptans, can be used.

The graft copolymer (B), which is the other component of thethermoplastic resin composition of the present invention and is added asan impact strength-increasing agent, is prepared by adding 15 to 50parts by weight of a monomer mixture of one or more of aromatic vinylcompounds, vinyl cyanide, methacrylic acid alkyl esters, and acrylicacid alkyl esters to 50 to 85 parts by weight of a butadiene-basedrubber or alkyl acrylate-based rubber and then polymerizing the monomermixture in the presence of the butadiene-based rubber or alkylacrylate-based rubber. The butadiene-based rubber or alkylacrylate-based rubber may contain small amounts of cross-linking agentsand chain transfer agents. At the time of graft polymerization, smallamount of crosslinking agents or chain transfer agents may beincorporated.

Aromatic vinyl compounds which can be used as the graft component forthe graft polymer (B) of the present invention include styrene,α-methylstyrene, chlorostyrene, tert-butylstyrene, and p-methylstyrene.Of these compounds, styrene is most preferred. As the vinyl cyanide,acrylonitrile is most preferred. In addition, methacrylonitrile can beused. Preferred examples of methacrylic acid alkyl esters are thosecompounds in which the alkyl group has from 1 to 4 carbon atoms, such asMMA, n-butyl methacrylate and ethyl methacrylate. Preferred examples ofacrylic acid alkyl esters are those compounds in which the alkyl grouphas from 1 to 8 carbon atoms, such as methyl acrylate, ethyl acrylate,and butyl acrylate.

The graft component as used herein is at least one monomer selected fromthe group consisting of the above-described aromatic vinyl compounds,vinyl cyanides, methacrylic acid alkyl esters and acrylic acid alkylesters. In order to increase the effect to impart high impactresistance, the graft component preferably comprises 0 to 100% by weightof a methacrylic acid alkyl ester and/or an acrylic acid alkyl ester, 0to 85% by weight of an aromatic vinyl compound, and 0 to 40% by weightof a vinyl cyanide. Typical examples are a styrene-acrylonitrilemixture, methyl methacrylate alone, a methyl methacrylate-styrenemixture, and a methyl methacrylate-styrene-acrylonitrile mixture.

The butadiene-based rubber to be used as the rubber component for thegraft copolymer (B) is polybutadiene or a butadiene copolymer preparedfrom a major proportion of butadiene and one or more vinyl monomerscopolymerizable with butadiene. Similarly, the alkyl acrylate-basedrubber is a polyalkyl acrylate or an alkyl acrylate copolymer preparedfrom a major proportion of alkyl acrylate and one or more monomerscopolymerizable with alkyl acrylate. Preferred examples of alkylacrylate are those compounds in which the alkyl group has from 4 to 8carbon atoms, such as butyl acrylate and octyl acrylate.

Cross-linking agents which can be used in the polymerization of therubber or graft component are those compounds copolymerizable withbutadiene or alkyl acrylates. Examples are divinylbenzene, ethyleneglycol dimethacrylate, diethylene glycol dimethacrylate, triethyleneglycol dimethacrylate, tetraethylene glycol dimethacrylate, ethyleneglycol diacrylate, diethylene glycol diacrylate, triethylene glycoldiacrylate, trimethyolpropane trimethacrylate or acrylate,1,3-butanediol dimethacrylate, and 1,3-butanediol diacrylate.

As chain transfer agents, known compounds such as n-octylmercaptan,n-dodecylmercaptan, and tertdodecylmercaptan can be used.

The graft copolymer (B) can be prepared by polymerization proceduresthat are commonly used. Especially preferred is an emulsionpolymerization method. To more improve the impact resistance of thecomposition, it is preferred to use a rubber latex having a meansparticle size of at least 1,500 Å. This rubber latex can be prepared byknown emulsion polymerization procedures. Such large particle sizedrubber latexes can be prepared by known techniques such as a multi-stageseed polymerization method and a microcoagulation method in which smallparticle sized rubber latexes are coagulated with additives such asacids, salts, and water-soluble polymers. The micro-coagulation methodis simpler in operation to conduct. Microcoagulation can be carried outby known procedures using inorganic acids such as hydrochloric acid,organic acids such as tartaric acid, malic acid and acetic acid,water-soluble polymers such as polyethylene oxide and polyvinyl alcohol,salt, metal salts such as magnesium chloride, combinations of peroxidesand formaldehydesulfoxylic acid salts, and the like.

With regard to the ratio of the rubber component to the graft component,the graft copolymer (3) is prepared from 50 to 85 parts by weight of therubber component and 15 to 50 parts by weight of the graft component(the sum of the rubber and graft components is 100 parts by weight) inorder to increase the effect of imparting impact resistance and furtherto facilitate post-treatments such as salting and drying. Graftpolymerization may be performed in either one stage or more stages.Moreover, it may be performed while continuously feeding the monomermixture.

Physical properties such as heat resistance and impact resistance of thethermoplastic resin composition of the present invention varysignificantly depending on the composition of each of the copolymer (A)and the graft copolymer (B) and further on the ratio of the copolymer(A) to the graft copolymer (B). In order that the physical propertiesare well balanced, the thermoplastic resin composition of the presentinvention is formulated to be composed of 50 to 90% by weight of thecopolymer (A) and 10 to 50% by weight of the graft copolymer (B).

The copolymer (A) and the graft copolymer (B) can be mixed by knownprocedures. For example, the copolymer (A) and the graft copolymer (B)are powdered or pelletized and are mixed by the use of rolls, screws,kneaders, Banbury mixers, and so forth. In addition, a method can beused in which the latexes of the copolymer (A) and the graft copolymer(B) are mixed and then salted out.

If desired, after the copolymer (A) and the graft copolymer (B) aremixed, additives conventionally used in such compositions, such asantioxidants, stabilizers, fillers, pigments, and plasticizers, can beadded to the resulting resin composition.

The thermoplastic resin composition of the present invention is superiorin heat resistance, impact resistance, mechanical characteristics andworkability and, therefore, is useful as a material for use in injectionmolding and extrusion molding.

The following Examples and Comparative Examples are given to illustratethe present invention in greater detail. In these Examples, the solutionviscosity (η_(sp/c)) was measured under conditions of solventchloroform, concentration 4 g/l, and temperature 30° C. The glasstransition temperature (Tg) was measured in a nitrogen (N₂) atmosphereat a rate of elevation of temperature of 10° C./min by the use of adifferential scanning calorimeter (DSC) produced by Rigaku Denki Co.,Ltd. The latex particle size was measured by the use of CoulterNano-sizer produced by Coulter Electronics, Ltd. All percents and partsare by weight and temperatures in degrees centigrade unless otherwiseindicated.

EXAMPLES 1 TO 8 AND COMPARATIVE EXAMPLES 1 TO 5 Preparation ofCopolymers A-1 to A-6

A polymerization reactor was charged with compounds as shown below and,after replacement of the atmosphere with N₂, they were heated to 60° C.in a stream of N₂.

    ______________________________________                                                                Amount                                                Component               (parts)                                               ______________________________________                                        H.sub.2 O               250                                                   Sodium Formaldehydesulfoxylate                                                                        0.4                                                   Sodium Dodecylbenzenesulfonate                                                                        1.5                                                   Ferrous Sulfate         0.0025                                                Disodium Ethylenediaminetetraacetate                                                                  0.01                                                  ______________________________________                                    

Monomer mixture as shown in Table 1 were each continuously introducedinto the polymerization reactor over 6 hours. After the addition wascompleted, the resulting mixture was further stirred at 60° C. for 1hour.

Each latex as prepared above was salted out with aluminum sulfate,neutralized, washed with water, filtered off, and extracted withmethanol to remove the remaining monomers. The thus-prepared copolymerwas measured for yield, glass transition temperature, and solutionviscosity. The results are shown also in Table 1. Copolymers A-5 and A-6are comparative copolymers not containing 2-IPN. It can be seen fromTable 1 that when 2-IPN is used as a copolymer component, the glasstransition temperature of the resulting copolymer (A) is greatlyincreased.

                                      TABLE 1                                     __________________________________________________________________________            Composition of Monomer Mixture                                                                       Yield                                                                             Tg η.sub.sp/c                          Copolymer (A)                                                                         α-MeSt                                                                       2-IPN AN MMA t-DM*.sup.2                                                                        (%) (°C.)                                                                     (dl/g)                                                                            Remarks                             __________________________________________________________________________    A-1     55   15 (21.4)*.sup.1                                                                    30 --  0.1  95  140                                                                              0.74                                                                              CHP*.sup.3 0.4                      A-2     65   10 (13.3)                                                                           25 --  0.2  88  144                                                                              0.71                                                                              "                                   A-3     55   20 (26.7)                                                                           25 --  0.1  87  148                                                                              0.64                                                                              "                                   A-4     62.5 11 (15.0)                                                                           17.5                                                                             9   0.15 91  146                                                                              0.59                                                                              "                                    A-5+   70    0 (0)                                                                              30 --  0.3  94  133                                                                              0.82                                                                              "                                    A-6+   75    0 (0)                                                                              25 --  0.3  88  138                                                                              0.77                                                                              "                                   __________________________________________________________________________     *.sup.1 The figures in parentheses indicate the percent of 2IPN based on      the total weight of MeSt and 2IPN.                                            *.sup.2 tDM: Tertdodecylmercaptan                                             *.sup.3 CHP: Cumene hydroperoxide (polymerization catalyst)                   +Comparative, not according to the invention.                            

Preparation of Copolymers A-7 and A-8

A polymerization reactor was charged with an aqueous solution containingthe same polymerization aids as used in the preparation of CopolymersA-1 to A-6. After replacement of the atmosphere with N₂, the contentswere heated to 60° C. in a stream of N₂. A monomer mixture (a) as shownin Table 2 was introduced into the polymerization reactor and thoroughlyemulsified. Then, a monomer mixture (b) as shown in Table 2 wascontinuously introduced over 6 hours. After the addition was completed,the mixture was further stirred at 60° C. for 1 hour. The thus-preparedlatex was subjected to the same post-treatment as in the preparation ofCopolymers A-1 to A-6.

The thus-prepared copolymer was measured for the yield, glass transitiontemperature, and solution viscosity. The results are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                       Copolymer                                                                     A-7       A-8                                                  ______________________________________                                        Monomer Mixture (a)                                                           α-MeSt     62.5        75                                               2-IPN            12.5 (16.6) 0                                                TDM              0.2         0.2                                              Monomer Mixture (b)                                                           AN               25          25                                               CHP              0.5         0.5                                              TDM              0.17        0.2                                              Yield (%)        91          92                                               Tg (°C.)  145         139                                              η.sub.sp/c (dl/g)                                                                          0.70        0.79                                             ______________________________________                                    

It can be seen from Table 2 that when a small amount of 2-IPN iscopolymerized, the glass transition temperature (Tg) of the resultingcopolymer is increased.

Preparation of Graft Copolymers B-1 and B-2

The Graft Copolymer B-1 was prepared as follows: The following compoundswere placed in a polymerization reactor and polymerized at 60° C. for 10hours.

    ______________________________________                                                             Amount                                                                        (parts)                                                  ______________________________________                                        Water                  170                                                    FeSO.sub.4.7H.sub.2 O  0.00195                                                EDTA.Na                0.00325                                                Sodium Pyrophosphate   0.1085                                                 Sodium Formaldehydesulfoxylate (SFS)                                                                 0.03                                                   Potassium Oleate (OLK) 0.9                                                    Butadiene (Bu)         55                                                     Styrene (St)           10                                                     TDM                    0.195                                                  CHP                    0.12                                                   ______________________________________                                    

The above-prepared rubber latex had a particle size of 820 Å.

The temperature of 236.3 parts of the rubber latex (rubber content: 65parts) was raised to 60° C., and 5 parts of 8.8% aqueous solution of SFSand 0.65 parts of a 355% aqueous solution of hydrogen peroxide wereadded thereto. The resulting mixture was stirred for 5 minutes and thenstirring was stopped. After 2.5 hours, 9 parts of a 3% aqueous solutionof NaOH, 0.5 part of OLK and 100 parts of H₂ O were added, and the pHwas 11.5. The latex rubber particle size as determined by the Nano-sizerwas 2,600 Å.

To the micro-coagulated rubber latex were added 12.25 parts of methylmethacrylate (MMA), 5.25 parts of St, 0.088 parts of TDM, 0.06 part ofCHP, 0.15 part of SFS, and 1 part of H₂ O, which were then polymerizedat 60° C. for 4 hours. In addition, 12.25 parts of MMA, 5.25 parts ofSt, 0.088 of TDM, 0.06 part of CHP, 0.03 part of SFS, and 0.2 part of H₂O were added to the rubber latex, and polymerization was continued at60° C. for 7 hours. Three hours after the start of the polymerization,0.03 part of SFS and 0.2 part of H₂ O were added.

A small amount of phenol-based antioxidant was added. On addinghydrochloric acid, precipitation occurred, yielding an MMA-St-Bu GraftCopolymer B-1. Tye yield was 99%.

The Graft Copolymer B-2 was prepared as follows: To the samemicro-coagulated rubber latex as used in the preparation of the GraftCopolymer B-1 in the amount of rubber content 65 parts were added 0.065part of dioctyl sodium sulfosuccinate, 12.25 parts of MMA, 5.25 parts ofSt, 0.088 part of TDM, 0.06 part of CHP, 0.15 part of SFS, and 1 part ofH₂ O, which were then polymerized at 60° C. for 6 hours.

In addition, 13.1 parts of St, 4.4 parts of AN, 0.088 parts of TDM, 0.06part of CHP, 0.03 part of SFS, and 1 part of H₂ O were added to thelatex, and polymerization was continued at 60° C. for 7 hours. Threehours after the start of the polymerization, 0.03 part of SFS and 1 partof H₂ O were added.

The same post-treatment as in the preparation of the Graft Copolymer B-1was applied, yielding an AN-MMA-St-Bu graft copolymer (Graft CopolymerB-2). The yield was 98.5%.

Physical Properties of the Resin Compositions

Resin compositions of 69.2 parts of Copolymer (A) and 30.8 parts ofGraft Copolymer (B) as shown in Table 3 were each roll-kneaded at 200°C. for 3 minutes and then press-molded at 220° C. Each mold was measuredfor Izod impact strength (according to ASTM-256; thickness: 6mm; Vnotch: R=0.25 mm), Vicat softening temperature (according to ASTMD-1525; load: 1 kg), and melt viscosity (using a Koka type flow tester;temperature: 260° C.; load: 100 kg; nozzle: 1.0 mm (diameter)×10 mm(length)). The results are shown in Table 3.

                                      TABLE 3                                     __________________________________________________________________________                            Izod Impact                                                                          Vicat                                                            Graft Strength                                                                             Softening                                                                            Melt                                                Copolymer                                                                           Copolymer                                                                           (23° C.)                                                                      Temperature                                                                          Viscosity                               Run No.     (A)   (B)   (kg-cm/cm)                                                                           (°C.)                                                                         (poises)                                __________________________________________________________________________    Example 1   A-1   B-2   13     141    --                                      Example 2   A-2   B-1    8     143    9.4 × 10.sup.3                    Example 3   A-2   B-2   16     143.5  --                                      Example 4   A-3   B-2   11     146.5  --                                      Example 5   A-4   B-1    8     147    7.0 × 10.sup.3                    Example 6   A-4   B-2   11     147.5  --                                      Comparative Example 1                                                                     A-5   B-2   24     132.5  --                                      Comparative Example 2                                                                     A-6   B-1   11     135.5  6.8 × 10.sup.3                    Comparative Example 3                                                                     A-6   B-2   22     136    --                                      Example 7   A-7   B-1   11     145     11 × 10.sup.3                    Example 8   A-7   B-2   16     145.5  --                                      Comparative Example 4                                                                     A-8   B-1   18     139     10 × 10.sup.3                    Comparative Example 5                                                                     A-8   B-2   19     139    --                                      __________________________________________________________________________

It can be seen from Table 3 that the compositions prepared using thematrix copolymers containing 2-IPN are superior in heat resistance tothe compositions using the matrix copolymers not containing 2-IPN.

EXAMPLES 9 AND 10 Preparation of Copolymer A-9

The same procedures as used in the preparation of the Copolymers A-7 andA-8 were repeated wherein 70 parts of α-MeSt, 10 parts of 2-IPN, and 0.1part of TDM were charged and fully emulsified and, thereafter, 20 partsof AN, 0.5 part of CHP and 0.1 part of TDM were continuously added over6 hours, whereupon Copolymer A-9 was prepared.

For the Copolymer A-9, the yield was 90%, the glass transitiontemperature (Tg) was 145° C., and the solution viscosity (η_(sp/c)) was0.71 dl/g.

Copolymer A-9 and the Graft Copolymer B-2 were compounded in the ratioshown in Table 4, roll-kneaded at 200° C. and then press-molded at 220°C. This mold was measured for the same physical properties as inExamples 1 to 8. The results are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                                        Graft                                                                 Copol-  Copol-   Izod Impact                                                                              Vicat                                             ymer    ymer     Strength   Softening                                         (A)     (B)      (notched, 23° C.)                                                                 Temperature                               Run No. (parts) (parts)  (kg-cm/cm) (°C.)                              ______________________________________                                        Example 9                                                                             69.2    30.8     14         144.5                                     Example 10                                                                            76.9    23.1     10         146                                       ______________________________________                                    

EXAMPLE 11 Preparation of Graft Copolymer B-3

The following compounds were placed in a polymerization reactor andpolymerized at 60° C. for 9 hours.

    ______________________________________                                                               Amount                                                                        (parts)                                                ______________________________________                                        Water                    170                                                  FeSO.sub.4.7H.sub.2 O    0.00195                                              EDTA.Na                  0.00325                                              Sodium Pyrophosphate     0.1085                                               SFS                      0.03                                                 OLK                      0.9                                                  Butyl Acrylate           70                                                   Ethylene Glycol Dimethacrylate (EDMA)                                                                  0.75                                                 Diisopropylbenzene Hydroperoxide (HPO)                                                                 0.12                                                 ______________________________________                                    

The resulting rubber latex was micro-coagulated at 60° C. with anaqueous hydrochloric acid solution to prepare a rubber latex having aparticle size (as determined by the use of the Nano-sizer) of 2,200 Å.

To the thus-micro-coagulated rubber latex were added 3.75 parts of MMA,8.25 parts of St, 3 parts of AN, 0.03 part of EDMA, 0.06 part of HPO,0.03 part of SFS, and 1 part of H₂ O which were then polymerized at 60°C. for 4 hours. In addition, 13.5 parts of MMA, 1.5 parts of St, 0.02part of EDMA, 0.03 part of HPO, 0.015 part of SFS, and 1 part of H₂ Owere added to the latex, and polymerization was continued at 60° C. for6 hours.

On applying acid-precipitation followed by drying and alkylacrylate-based rubber-containing graft copolymer was obtained.

The Copolymer A-9 and the Graft Copolymer B-3 were compounded in a ratioof A-9/B-3=65/35, and then roll-kneaded and press-molded in the samemanner as in Examples 1 to 8. This mold was measured for the physicalproperties. The Izod impact strength (notched, 23° C.) was 6 kg-cm/cmand the Vicat softening temperature was 142° C.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A thermoplastic resin composition exhibitingimproved heat resistance and high impact resistance, comprising:50% to90% by weight of a copolymer (A) prepared by copolymerizing of 10 to 35%by weight of acrylonitrile, 60 to 85% by weight of a monomer mixtureconsisting of 2-Isopropenylnaphthalene and α-methylstyrene, theproportion of 2-isopropenylnaphthalene being 5% to 70% by weight basedon the total of 2-isoprophenyl- naphthalene and α-methylstyrene, and 0to less than 10% by weight of a vinyl monomer copolymerizable with theforegoing monomers; and 10 to 50% by weight of a graft copolymer (B)prepared by adding 15 to 50 parts by weight of at least one monomerselected from the group consisting of aromatic vinyl compounds, vinylcyanides, methacrylic acid alkyl esters, and acrylic acid alkyl estersto 50 to 85 parts by weight of an alkyl acrylate-containing rubber, thesum of the rubber component and the graft component being 100 parts byweight, and polymerizing the graft copolymer in the presence of therubber component.
 2. The thermoplastic resin composition of claim 1, inwhich the total monomer mixture of copolymer (A) contains from 65 to 80%by weight of 2-isopropenylnaphthalene and α-methylstyrene.
 3. Thethermoplastic resin composition of claim 1, in which the proportion of2-isopropenylnaphthalene is from 10 to 60% by weight based on the totalweight of 2-isopropenylnaphthalene and α-methylstyrene.
 4. Thethermoplastic resin composition of claim 1, in which the total monomermixture of copolymer (A) contains from 15 to 30% by weightacrylonitrile.
 5. The thermoplastic resin composition of claim 1, inwhich copolymer (A) contains at least one of styrene, methylmethacrylate, methacrylonitrile, methacrylic acid or acrylic acid as thevinyl monomer component.
 6. The thermoplastic resin composition of claim1, in which the methacrylic acid alkyl esters in the graft component ofa graft copolymer (B) have an alkyl group containing 1 to 4 carbonatoms.
 7. The thermoplastic resin composition of claim 1, in which theacrylic acid alkyl esters in the graft component of a graft copolymer(B) has an alkyl group containing 1 to 8 carbon atoms.
 8. Thethermoplastic resin composition of claim 1, in which the graft componentof graft copolymer (B) contains:0to 100% by weight of a methacrylic acidalkyl ester, an acrylic acid alkyl ester or mixtures thereof; 0 to 85%by weight of an aromatic vinyl compound; and 0 to 40% by weight of avinyl cyanide.
 9. The thermoplastic resin composition of claim 1, inwhich the rubber component of graft copolymer (B) is a polyalkylacrylate or an alkyl acrylate copolymer containing a major proportion ofan alkyl acrylate and the balance at least one monomer copolymerizabletherewith, provided that the alkyl group of the alkyl acrylate employedcontains from 4 to 8 carbon atoms.
 10. A molded article of thethermoplastic resin composition of claim 1.